What Type of Exercise is Best for Getting Lean?
This space has been utilized for the purpose of nutrition and diets, but the subjects of diet and exercise are so thoroughly entwined that I thought I would spend a few words on the effect of aerobic versus anaerobic exercise as it pertains to body fat loss. These two terms are generally used to describe strength training (anaerobic) and what most people mistakenly refer to as cardio (aerobic), such as walking, jogging, stationary bike etc., where the heart rate is kept relatively low and steady for an extended period of time. Lets define both before we delve into which would better help you achieve your weight loss goals. The following is the biochemistry (hang with me here) of these energy systems.
These two terms refer to energy systems that our bodies utilize to fuel the muscle contractions that occur during all types of exercise. The fuel is called ATP (adenosine triphosphate). The Anaerobic system may be further divided into the phosphagen system that will last 14-20 seconds and the glycolitic/lactic acid system which takes over for the next several minutes depending on the intensity of the exercise. Prolonged exercise of low intensity will eventually exceed your body’s ability to produce ATP molecules from glucose or lactic acid, resulting in fat being burned in the mitochondria in the presence of oxygen, or, aerobic activity. An exercise may be both anaerobic and aerobic. Let me explain.
I will use running as our exercise, and our healthy, injury-free exerciser has warmed up by walking for a few minutes then jogged for a couple more. Our runner takes a one minute break, then begins to sprint. The initial fuel is a substance called creatine phosphate (CP) that is available for immediate use for approximately 6-8 seconds. Your body can immediately produce more from ATP stored in the muscle to give you another 8-12 seconds of sprinting for a total of approximately 14-20 seconds of maximal intensity. At this point you will begin to slow. Your body will now switch to the other anaerobic system which is actually two distinct sytems, glycolysis and lactic acid.
Glycolysis uses available blood sugar (glucose) in the blood stream and then the storage form (glycogen) from your muscle and liver to produce a substance called pyruvic acid, which is then converted to ATP molecules to be used in the muscle. At some point this system cannot keep up with demand, due to glucose depletion and/or oxygen debt, and the pyruvic acid is converted to lactic acid and diffuses out of the muscle into the bloodstream. Later, when oxygen is again available, the lactic acid will be reconverted back to pyruvic acid to be used by the muscles to produce ATP.
If you were to continue to exercise without adequate recovery of glucose or oxygen, you will begin utilizing the aerobic system, where fatty acids enter the mitochondria and, through a series of chemical reactions, produce ATP for the exercising muscles. This only happens with very low intensity, long duration forms of exercise. If the aerobic system is burning fatty acids for its primary fuel source, then this would be the most efficient way to get leaner right? Not necessarily.
If you jog a mile on relatively flat terrain you will burn approximately 100-140 calories depending on several variables including bodyweight and composition as well as efficiency of motion and stride length. If you average 5 miles per hour, you will expend approximately 500-550 calories per hour for a 130 lb female, 650-700 for a 200 lb male. That is a very good rate of expenditure. If you perform high intensity weight training for an hour with no more than a 60 second rest interval between sets you will expend about the same amount of calories. That number rises 25%-30% if you cut the rest break to 40 seconds.
The most pronounced difference between the two forms of exercise is the effect on body composition. Strength training has the capacity to induce muscle hypertrophy, or thickening of the muscle fibers. These enlarged muscle fibers are more metabolically active, requiring additional calories to sustain them while at rest. Aerobic exercise has virtually no capacity to hypertrophy muscle mass, in some cases inducing atrophy or a loss of lean muscle mass and in turn lowering your resting metabolic rate. This difference is stark and significant!
To summarize, if you want get lean and in the process increase your body’s rate of calorie expenditure, get in the weight room and add some muscle.